1. The Field of the Invention
The present invention relates generally to optoelectronic components. More particularly, the present invention relates to circuitry for controlling the temperature of a laser emitter.
2. The Relevant Technology
FIG. 1 shows a schematic representation of the essential features of a typical prior-art fiber optic transceiver. The main circuit 1 contains at a minimum transmit and receiver circuit paths and power 19 and ground connections 18. The receiver circuit typically consists of a Receiver Optical Subassembly (ROSA) 2 which contains a mechanical fiber receptacle and coupling optics as well as a photodiode and pre-amplifier (preamp) circuit. The ROSA is in turn connected to a post-amplifier (postamp) integrated circuit 4, the function of which is to generate a fixed output swing digital signal which is connected to outside circuitry via the RX+ and RX− pins 17. The postamp circuit also often provides a digital output signal known as Signal Detect or Loss of Signal indicating the presence or absence of suitably strong optical input. The Signal Detect output is provided as an output on pin 20. The transmit circuit will typically consist of a Transmitter Optical Subassembly (TOSA), 3 and a laser driver integrated circuit 5. The TOSA contains a mechanical fiber receptacle and coupling optics, as well as a laser diode or LED. The laser driver circuit will typically provide AC drive and DC bias current to the laser. The signal inputs for the AC driver are obtained from the TX+ and TX− pins 12. Typically, the laser driver circuitry will require individual factory setup of certain parameters such as the bias current (or output power) level and AC modulation drive to the laser. This is frequently accomplished by adjusting variable resistors or placing factory selected resistors 7, 9 (i.e., having factory selected resistance values). Additionally, temperature compensation of the bias current and modulation is often required. This function can be integrated in the laser driver integrated circuit or accomplished through the use of external temperature sensitive elements such as thermistors 6, 8.
In addition to the most basic functions described above, some transceiver platform standards involve additional functionality. Examples of this are the TX disable 13 and TX fault 14 pins described in the GBIC (Gigabit Interface Converter) standard. In the GBIC standard (SFF-8053), the TX disable pin 13 allows the transmitter to be shut off by the host device, while the TX fault pin 14 is an indicator to the host device of some fault condition existing in the laser or associated laser driver circuit. In addition to this basic description, the GBIC standard includes a series of timing diagrams describing how these controls function and interact with each other to implement reset operations and other actions. Most of this functionality is aimed at preventing non-eyesafe emission levels when a fault condition exists in the laser circuit. These functions may be integrated into the laser driver circuit itself or in an optional additional integrated circuit 11. Finally, the GBIC standard for a Module Definition “4” GBIC also requires the EEPROM 10 to store standardized serial ID information that can be read out via a serial interface (defined as using the serial interface of the ATMEL AT24CO1A family of EEPROM products) consisting of a clock 15 and data 16 line.
In the above referenced patent applications entitled “Compact Laser Package With Integrated Temperature Control” and “Optoelectronic Module with Thermally Isolated Components,” temperature controllers are integrated within an optoelectronic module and/or a laser package itself It is difficult to implement the temperature control functionality for such controllers using the prior art control circuitry.
Accordingly, circuitry for controlling temperature regulators of an optoelectronic device is needed.